When some individuals take up considerably more speaking time than others, it is possible and necessary to intervene in a number of ways. The intervention should aim to encourage those who speak up less to be freer and more active, and the choice of method can be crucial here, while on the other hand, you want to encourage those who take up more than their fair share of speaking time to become aware of this uneven distribution. Whichever intervention you opt for, it should be encouraging rather than restrictive, because the point is not to have someone who had been speaking up more suddenly withdraw, but rather to ensure that there is mutual respect within the group. Since it is common to invoke the principle of “shared time” in the initial agreement, which includes responsibility for both being punctual and using this shared time, you can invoke this rule or suggest including it, if it has not already been introduced into the agreement.